Door lock



Patented Mar. 17, i1953 DOOR LOCK Headley Townsend Backhouse, Sunnngdale, England Application November 9, 1949, Serial No. 126,266 In Great Britain November 17, 1948 3 claims.

This invention relates to door locks (i. e. locks for doors and like hinged closure members) of the type comprising a sliding latch bolt (hereinafter referred to as a latch bolt or as a bolt) mounted in a housing secured to or provided in the door and for co-operation with a keeper secured to or formed in the jamb post of the door-way, a slide (which may be formed integrally with the bolt) operable by a handle or knob from either side of the door to withdraw the latch bolt to the unlatched position and a spring co-operating with the slide or the bolt to urge-the latter towards the latching position. In locks of the type described the outer end of the bolt is usually formed with a bevelled face to engage a lip on the keeper so that when the door is swung towards the closure position the bolt will readily ride over the keeper being pushedv inwardly thereby until it is in register with the keeper socket when it will be forced home to locking position by its spring.

It has already been proposed (see the applicants United States Patent No. 2,174,958 and his British patent specification No. 496,776 dated December 2, 1937) to provide a door lock of the type described above having in combination two positive locking devices independently movable from the two sides of the doors respectively to lock the latch bolt positively in the latched position and a stop member (e. g. a ball or a swinging lever) which as one locking device is operated to lock the latch, is moved, by the locking device, into the path of the other locking device thereby to prevent the second device also being moved to the locking position.

According to the present invention a lock of the above type having a stop member as just de- -scribed is characterised by means whereby the stop member may, as an alternative to movement as aforesaid, be preset in the path of one or other of the locking devices to prevent operation of that device.

The invention is especially suited for application to locks, as described in the applicants United States patent and British patent specification hereinbefore mentioned having two independently operable handles (one for each side of the door or the like) each of which can be moved in one direction to force the slide to withdraw the latch bolt into the unlatching position or moved in the other direction to place a positive abutment in the path of the slide so as to lock the latch bolt in the latching position.

The invention is preferably applied to that form of lock of the type described in which each locking device comprises, as disclosed in said United States patent or British patent specification, an arm extending radially from a rotatable hub or spindle arranged for rotation by an associated handle to move the arm from a neutral position, in one direction to move the slide to the unlatching position and in the other direction to a position in which it serves as a strut preventing withdrawal of the slide to the unlatching position. It is a preferred feature of the invention when so applied that the slide has a bearing surface Which, if the latch bolt is not fully extended and home in the keeper, is engaged by a locking arm as it is moved towards the locking position, with a cam action tending to force the latch bolt home.

When the locking devices comprise radial arms as above described, the two arms may be substantially parallel to one another and spaced apart to a small extent and the stop member may consist of a wedge directed between the two arms and arranged for a swinging movement about an axis near its base so that either arm as it is moved to the locking position engages one Wedge face and diverts the member into the path of the other arm unless it has, as aforesaid, been pre-set in the path of one of the arms` The wedge may be mounted on a spindle arranged for manual rotation from the outside of the lock casing (e. g. at the front of the casing) to move the wedge so that it may be pre-set to a position in which it lies in the path of either of the locking arms to prevent that arm from being moved to the locking position. Means may be included for retaining the wedge in such a preset position.

One specific construction of lock according to the invention will now be described by way of example and with reference to the accompanying drawings which are largely diagrammatic and in which:

Figure 1 is a perspective view with the lock cover removed and the casing partly broken away, this figure showing the latch in the fully extended position, Y

Figure 2 is a view similar to Figure 1 but showing the latch being forced home by operation of one of the locking arms,

Figure 3 shows the latch locked, and

Figure 4 is a part section in the direction 4-4 in Figure 1 but modified to show one of the arms in the locking position.

The lock forming the subject of this example comprises a casing l within which is housed a slide 2 carrying a latch bolt head 3 which may be withdrawn from the casing against the action of a spring 4 to enable the aspect of the head to be reversed. A spring 5 extends into a socket in the slide and urges the slide into the latching position (i. e. the position shown in Figure 1). Two locking arms 6 and 1 are provided and are secured to hubs 8 independently rotatable from opposite sides of the lock by handles having square shanks fitting into sockets 9. Leaf-springs I urge the arms 5 and I anticloekwise into the position shown in Figure 1 and, when the arms have been moved further in the anticlockwise direction into the position shown in Figure 3, serve as detents to hold the arms in that position.

Movement of either arm 6 or 'I in the clockwise direction from the Figure 1 position withdraws the slide 2 and latch bolt` head 3Y into the unlatching position. When either arm El or I is moved in the anticlockwise direction into the position shown in Figure 3 the arm serves as a positive stop preventing withdrawal of the slide 2 into the unlatching position. It sometimes happens that owing for example to friction in the keeper, the slide 2 is not forced fully home by the spring. It is however essential that the slide shall be fully home before a locking arm 6 or 7 can be moved into the locking position and Figure 2 shows how the movement of an arm towards' that position effects a preliminary engagement with a bearing surface constituted by a stop I I on the slide 2 so that further movement of the arm forces the slide to the latching position.

In practice it is important that it should be impossible for both arms 6 and 'I to be moved to the locking position at the same time. vent this occurrence there is provided a lozenge shaped stop member I2 vwhich has a wedge form normally directed between the two arms 5 and 7. The member I2 is secured to a spindle I3 of spring wire which permits a limited degree oi rotation of the member by torsion ofthe wire. Ii either of the locking arms 6 or 'I is moved into the locking position, the arm engages the top wedge form of the member I2 and forces the member to one side into the path of the other arm. Figure 4 shows the arm 'I moved to the locking position and the member I2 rotated into the path of the other arm E. It is then impossible to move the second arm E to the locking position.

The spindle I3 is extended outwardly through a hole in the front plate I4 of the lock and is then cranked to provide a tang fitting into any one of three holes i5. A spring i5 surrounds the spindle and tends to hold the tang in the selected hole. If for any reason it is desired to prevent movement of one handle to the locking position (e. g. if the lock is to be used on a bathroom door and it is desired to prevent the door being locked from the outside) the spindle I3 is rotated to bring the member l2 into the path of the appropriate locking arm 6 or 'I and thek tang is inserted into the appropriate hole. The lock is then preset to allow one handle to be moved into locking position as may be desired but to prevent movement of the other handle into locking position.

In the above example the thrust derived from an attempt to move a handle to the locking posi- To pretion when the other handle is already in the locking position is transmitted through the stop member I2 .to the bottom of the casing I. It is therefore necessary to ensure that the casing is suiiiciently strong to absorb this thrust and for this purpose the bottom of the casing must be stronger than is commonly the case in locks.

I claim:

1. In a door lock of the type which comprises a casing having a front plate, a latch bolt slidable within the casing and through said front plate into and out of locking position, two parallel spaced-apart actuating and locking arms within the casing movable independently by handles on opposite sides of the door and adapted when moved in onev direction to withdraw said boltv and when moved in the opposite direction t to hold said bolt in locking position, said arms in moving to locking position moving toward a wall of said casing; stop means adapted automaticallyto prevent one of said arms from being moved to locking position when the other of said` arms has been moved to that position and adapted to be pre-set to selectively prevent one of said arms from being moved to locking position and comprising: a stop member having a wedgeshaped end directed toward said arms and positioned with its base bearing against said wall of said casing, a torsion member mounted in said Vcasing and xed to and supporting said stop member adjacent its base and vhaving an end extending through said front plate, means external to said casing for rotating said torsion member and iixing it in `preselected positions in one of which positions the wedge-shaped end or" said stop member is normally directed toward thespace between said arms whereby actuation of either arm to locking position ,engages the stop member and moves it into the path of the other arm and in-another of said positions locates the wedge-shaped end of the stop member in the path of one of said arms and prevents its movement into locking position.`

2. A lock according to claimY 1 wherein said cranked arm has a tang directed toward said front plate and said front plate is provided with apertures to receive said tang.

HEADLEY 'I'OWNSEND` BACKHOUSE.

REFERENCES CITED The following references are of record in the le ofl this patent: v UNITEDKSTATEKS PATENTS Number Name Date Re. 22,230 Voight et al..` Dec. 1, 1942 1,038,512 Anderson Sept. 17,r 1912 Backhouse Oct. 3, 1939y 

